Dec '19. Above is a post from Ignasis saying he’d prompt the team to look into it. At the same time, another thread was dealing with the subject:
In the above “cleansing is bugged” thread, Ignasis seems a bit unsurprised that these weapons are working this way. Dec '19.
And finally, from the Mounts and Movement patch:
Look in Ignasis’s OP and find the word “cleansing.” It is specifically mentioned in the fix for Cleansing Brew, which is apparently intended to remove corruption. There are some inconsistencies, but I don’t think this means it takes forever for little things to get fixed.